Bearing ring for supporting items on solid or hollow cylindrical parts

ABSTRACT

The cylinder may be an aircraft landing gear axle. The items may be pick-ups the sense axle deformation. A ring (30) for supporting the pick-ups is made of highly resilient material. It is initially of such a size that its cylinder-engaging surface overlaps the cylindrical surface it is to engage. The ring is then deformed by urging at least two points (34 to 37) around its circumference to increase the degree of overlap. While maintaining the deforming force on the ring, its cylinder-engaging surface (31) is machined so that there is no longer any overlap, and still maintaining the force, the ring is engaged with the cylinder. The force is then removed. The said points move resiliently away from the cylinder, but intermediate points are consequently resiliently urged into contact with the cylinder. The contact is smooth and progressive, thus avoiding the kind of stress concentrations that could reduce cylinder life by fatigue, etc.

This is a division of application Ser. No. 602,642, filed Apr. 19, 1984,now U.S. Pat. No. 4,651,402 issued on Mar. 24, 1987.

The present invention relates to methods of making bearing ringsproviding support for items, such as pick-ups, for example, suitable forbeing disposed in the cylindrical inside portion of hollow parts, oraround the cylindrical outside portion of solid or hollow parts.

BACKGROUND OF THE INVENTION

In some applications, and in particular in aeronautics, and moreparticularly in the manfucture of undercarriages or landing gear, it issometimes necessary to place parts, such as force sensors, for example,on such landing gear in order to measure the deformations to whichvarious parts of the landing gear are being subjected. This possibilityis provided in particular, for forestalling various kinds of failure,and even, for measuring the total weight of an aricraft.

Of all these applications, one is of particular interest, namelymeasuring the total mass of an aircraft and/or its center of gravityand/or the stress to which its tires are subjected. This can be done,for example, by measuring the deformation of an axle in the aricraftlanding gear. The axle may be constituded by a hollow cylindrical part,in which case, electromagnetic or capacitive sensors may be placedinside the axle to measure the deformation thereof and thus to enablethe forces applied to the landing gear to be deduced. By analyzing a setof such forces, the mass of the aircraft can readily be deduced. This isof particular interest just prior to take off to see if the totalstarting weight is acceptable.

The problem to be solved is how to place such sensors inside an axle.Techniques known up to now have always suffered from drawbacks.

Two particular prior art techniques require:

Either providing at least two bearing regions on the axle for engagingsensor-supporting parts, with the bearing force resulting from theradial resilience of the axle and from screw displacement of one or moremoving parts on the sensor-supporting part. Since the radial resilienceof the axle is small, the bearing force is concentrated and variesgreatly when the axle is deformed under load, which is a potentialsource of breakage and of accident.

Or else cavities are made in the axle and balls are received in thecavities. The same problem of potential stress concentrations leading tocracking and breakage remains.

Preferred implementations the present invention mitigate these drawbacksby ensuring that the pressure applied in the bearing regions remainspractically constant in spite of possible deformation of the axle. Thisis achieved by using highly resilient bearing rings for supporting itemssuch as deformation sensors. Further, stress concentrations are avoided.

SUMMARY OF THE INVENTION

The present invention provides a method of making a bearing ring forsupporting an item inside a hollow cylindrical part in a first case, oroutside a solid or a hollow cylindrical part in a second case, themethod consisting in the following steps:

a first step of providing a ring of highly resilient material and havinga cylinder-engaging surface of a diameter that overlaps the diameter ofthe corresponding ring-engaging surface of the cylinder, i.e. in thefirst case the ring outside diameter is greater than the cylinder insidediameter, and in the second case the ring inside diameter is less thanthe cylinder outside diameter;

a second step of applying forces to at least two points round the ringto elastically deform the ring in such a manner that the said overlapincreases at said points, i.e. in the first case the ring outsidediameter is increased at the said points by the deformation, and in thesecond case the ring inside diameter is decreased at the said points bythe deformation;

a third step of machining the ring while still applying the said forcesthereto, the machining being applied to the said deformedcylinder-engaging surface of the ring so that there is no overlapbetween the diameter thereof and the diameter of the correspondingring-engaging surface of the cylinder, i.e. in the first case thedeformed outside diameter is reduced, and in the second case thedeformed inside diameter is increased;

a fourth step of engaging the machined ring with the cylinder whilestill applying the said forces thereto, i.e. placing the ring inside thecylinder in the first case, and around the cylinder in the second case;and

a fifth step of releasing the ring from the action of the said forces.

The invention also provides a bearing ring made by the above-definedmethod.

BRIEF DESCRIPTION OF THE DRAWINGS

An implemenation of the invention is described by way of example withreference to the accompanying drawings, in which:

FIG. 1 is a diagram of an aircraft landing gear suitable for receiving abearing ring in accordance with the invention for measuring, forexample, the deformation of an axle on which a wheel is mounted;

FIG. 2 is a cross section through a landing gear axle taken in a planeA--A of FIG. 1;

FIGS. 3A, 3B, 3C, 3D, 3E and 3F show different stages in the method ofpreparing a bearing ring in accordance with the invention; and

FIGS. 4A and 4B are a cross section and a longitudinal sectionrespectively through an application of a bearing ring in accordance withthe invention to supporting sensors inside an axle as shown in FIG. 1.This application is given merely by way of one example of one use for abearing ring in accordance with the invention.

MORE DETAILED DESCRIPTION

FIG. 1 shows the bottom portion of an aircraft landing gear 1, having aleg 2 with a bottom end 3 to which an axle is fixed. The axle is visibleat 4 and 5, and has running means 6 and 7 fixed to each end thereof. Therunning means is commonly in the form of a hub 8 and a pneumatic tire 9.

In some applications there is a need to know the total mass of anaricraft on the ground, so as to know its take off weight. Thisinformation can be deduced from measurements of the forces acting onsome of the axles on which ground-contacting wheels are mounted. Bycombining measurements from several axles, the total mass of theaircraft can be determined. The axle 4, 5 is generally made up of hollowcylindrical parts and/or hollow conical parts. FIG. 2 is a cross sectionthrough the axle portion 5 taken plane A--A of FIG. 1, it shows thehollow interior 10 of the axle 5. In many applications it isadvantageous to mask the equipment associated with the landing gear asmuch as possible, which is why any force pick-ups or sensors shouldpreferably be located inside the axle 5. In which case there is aproblem of how to fix the sensors or other parts in the axle interior10, e.g. on the axle wall 11.

The invention provides bearing rings which can be mounted inside such anaxle 5 and which co-operate suitably with the inside wall 11 thereofwithout causing damage. The following example concerns a bearing ringsuitable for mounting inside a hollow cylinder, but the person skilledin the art would have no difficulty in adapting the same method tomaking a ring for mounting on the outside of a cylindrical part when itis not possible to mount it on the inside. In other words the bearingring could be mounted on the outside wall 12, even though it isgenerally much preferred in aeronautics to mount it in the interior 10.

FIGS. 3A to 3F show different stages in the method of making a bearingring in accordance with the invention. Starting with FIG. 3A, a ring 30of highly resilient material which is advantageously made in a singleclosed piece, has an axle-contacting diameter which overlaps thecorresponding diameter of the axle 5. In other words, an inside-mountedbearing ring has an outside diameter 31 which is slightly greater thanthe diameter of the inside wall 11 of the axle 5, while an outsidemounted ring would have an inside diameter slightly smaller than theoutside wall 12. In some applications the ring is not closed, but is inopenable like a spring clip. The thickness 32 of the ring is determinedas a function of various considerations which the person skilled in theart will have no difficulty in determining for any given application.

Once the ring has been made, and keeping with the inside mountedexample, forces are applied at regularly spaced 90° intervals round theinside of the ring (see FIG. 3B) to deform the ring in an accuratelypredetermined manner which is explained below. In the specific exampleshown, the means 33 for applying the deforming forces comprise fourshoes 34, 35, 36, and 37 pivotally mounted on respective screws 38, 39,40, and 41 which co-operate with respective nuts 42, 43, 44, and 45which are themselves free to rotate relative to a base 46. Thus, byrotating the nuts, the screws are displaced along orthogonal axes 50 and51, thereby displacing the shoes 34 to 37.

Once the means 33 have been positioned in the ring 30, the shoes aremoved outwardly along the orthogonal axes 50 and 51 so as to increasethe ring diameter along these axes and so as to deform the ring into thecurvilinear shape shown in FIG. 3C. The deformation applied is such asto ensure that the inside diameter of the axle 5, i.e. the surface ofthe inside wall 11, remains within the thickness of the ring material asshown by a dashed line 52 in FIG. 3C. In other words, when the fourportions 53, 54, 55, and 56 of the ring are pushed outwardly, theintermediate portions half way between them tend to move inwardly andthus take up a smaller diameter than before.

Once the ring has been deformed to an extent which will generally bedefined by experiment, the deformed ring, while still subjected to thedeforming forces, is machined so that its axle-engaging surface is madeequal to to the diameter of the corresponding axle surface.Advantageously, the machining continues far enough to ensure that thereis no overlap at all. FIG. 3D shows an outside ring surface 57 which isof slightly smaller diameter then the cylindrical inside surface of theaxle inside wall 11. The excess metal outside the dashed line 52 in FIG.3C is removed by means of lathe, for example. The resulting ring asshown in FIG. 3D, and still subjected to the deforming force, is thuscapable of being inserted inside the axle 5 as shown in FIG. 3E.

Once the ring has been suitably positioned inside the axle 5, the means33 are released, i.e. the nuts are turned so that the shoes 34 to 37move radially inwardly. Its resilience will then cause the ring to tendtowards the opposite deformation, in other words the said intermediateportions 60, 61, 62 and 63 will press firmly against the wall of theaxle, while possibly leaving the previously outwardly urged points 53,54, 55 and 56 slightly clear of the inside wall 11 of the axle (theclearance has been exaggerated for clarity, while the dashed lines atthe points of pressure contact represent the envelope of the forcesapplied to the inside wall of the axle 5).

Under such conditions, the ouside surface of the ring has low amplitudecorrugations which nevertheless cause the ring to press resilientlyagainst four regions of the inside wall and thus hold the ring firmly inplace. In particular, there is no need to make grooves or notches in theinside surface of the axle which could seriously shorten the lifetime ofthe axle, i.e. by providing stress concentrations that are particularlydamaging in fatigue when high forces are applied to the axle as duringlanding.

The envelopes of the forces applied to the inside wall 11 of the axlevary smoothly, thus avoiding any damaging concentration of forces thatcould lead to a hairline cracks and ultimately to axle failure.

Thus, once a ring is placed inside an axle, all sorts of devices such aspick-ups may be mounted inside the axle by various means, includingconventional screws.

FIGS. 4A and 4B are respectively a cross section and a longitudinalsection through an axle 5 fitted with means for measuring axledeformation. There are two bearing rings 70 and 71 mounted inside theaxle, at a predetermined distance apart. Complemetary parts 73 and 74 ofa pick-up 72, e.g. a magnetic or a capacitive sensor, are mounted oneach ring. For example, the part 73 which is fixed to the ring 71 isplaced facing the part 74 which is constituted by an active plate. Whenthe axle is deformed the spacing between the pick-up parts varies by anamount which can readily be determined by the person skilled in the art.Given a variable distance separating the two parts of the pick-up,corresponding variations will occur in an electrical signal, which isduly transmitted to a calculator or computer on board the aircraft.

Advantageously, an outside surface of the ring where it makes contactwith the inside of the axle will be toroidal in shape, as is well known.

I claim:
 1. In combination, a metal bearing ring and a hollow metalcylindrical part supporting said ring outside or outside said hollowmetal cylindrical part, said bearing ring being formed and mounted tosaid hollow metal cylindrical part by the method comprising thefollowing steps:providing said ring of highly resilient metal having acylinder-engaging surface of a diameter that overlaps the diameter ofthe corresponding ring-engaging surface of said cylindrical metal part;applying localized forces to at least two circumferentially spacedpoints on the ring to locally, elastically deform the ring such thatsaid overlap increases at said points and wherein said overlap decreasesat other circumferentially spaced points intermediate said at least twocircumferentially spaced points; machining the deformed cylindricalpart-engaging surface of the ring while applying said localized forcesthereto during and after said machining, so that there is no overlapbetween the diameter thereof and the diameter of the correspondingring-engaging surface of said cylindrical part; engaging the machinedmetal ring against the metal cylindrical part while still applying saidlocalized forces thereto; and removing the applied forces; such thatbefore machining, a first set of exterior forces produces a series ofelastic deformations at certain points within said ring and a series ofreverse elastic deformations at said other points, and after machiningand after assembly, a second set of internal forces within said ringproduces a series of elastic deformations at said other circumferentialpoints defining on said surface of said ring abutting said hollow metalcylindrical part low amplitude corrugations which press resilientlyagainst said hollow metal cylindrical part at said other points withoutstress concentrations at said other points leading to an attendantfatigue damage to said metal bearing ring and metal cylindrical partassembly thereby insuring the deformation holding of the metal bearingring and hollow metal cylindrical part assembly.
 2. In combination, ametal bearing ring and a solid metal cylindrical part supporting saidring outside said solid metal cylindrical part, said bearing ring beingformed and mounted to said solid metal cylindrical part by the methodcomprising the following steps:providing said ring of highly resilientmetal having a cylinder-engaging surface of a diameter that overlaps thediameter of the corresponding ring-engaging surface of said cylindricalmetal; applying localized forces to at least two circumferentiallyspaced points on the ring to locally, elastically deform the ring suchthat said overlap increases at said points, and wherein said overlapdecreases at other circumferentially spaced points intermediate said atleast two circumferentially spaced points; machining the deformedcylindrical part-engaging surface of the ring while applying saidlocalized force thereto during and after said machining, so that thereis no overlap between the diameter thereof and the diameter of thecorresponding ring-engaging surface of said cylindrical part; engagingthe machined metal ring against the metal cylindrical part while stillapplying said localized forces thereto; and removing the applied forces;such that before machining, a first set of exterior forces produces aseries of elastic deformations at certain points within said ring and aseries of reverse elastic deformations at said other points, and aftermachining and after assembly, a second set of internal forces withinsaid ring produces a series of elastic deformations at said othercircumferential points, defining on said surface of said ring abuttingsaid hollow metal cylindrical part low amplitude corrugations whichpress resiliently against said hollow metal cylindrical part at saidother points without stress concentrations at said other points leadingto an attendant fatigue damage to said metal bearing ring and metalcylindrical part assembly thereby insuring the deformation holding ofthe metal bearing ring and solid metal cylindrical part assembly.